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Parasitic Infections from Eating Raw Crayfish

Infectious disease specialists at Washington University have diagnosed a rare parasitic infection in seven people who had eaten raw crayfish from Missouri streams and rivers. The unusual cases occurred over the past three years; four have been diagnosed since September 2009. Before these seven diagnoses, only seven such cases had ever been reported in North America, where the parasite, Paragonimus kellicotti, is common in crayfish.

“The infection, called paragonimiasis, is very rare, so it’s extremely unusual to see this many cases in one medical center in a relatively short period of time,” says Gary Weil, MD, Washington University infectious diseases specialist at Barnes- Jewish Hospital, who treated some of the patients. “We are almost certain there are other people out there with the infection who haven’t been diagnosed.”

Paragonimiasis causes fever, cough, chest pain, shortness of breath and extreme fatigue. The infection is generally not fatal, and it is easily treated with an oral drug, praziquantel. All the patients have completely recovered, even one who temporarily lost his vision when parasites invaded his brain.

The illness is so unusual that most doctors are not aware of it. The parasitic worms at the root of the infection primarily travel from the intestine to the lungs. They also can migrate to the brain, causing severe headaches or vision problems, or under the skin, appearing as small, moving nodules.

Diagnostic clues include elevated levels of eosinophils. X-rays also show excess fluid around the lungs and sometimes the heart.